Recycling of waste materials is highly desirable from many viewpoints, not the least of which are financial and ecological. Properly sorted recyclable materials often can be sold for significant revenue. Many of the more valuable recyclable materials do not biodegrade within a short period. Therefore, recycling such materials significantly reduces the strain on local landfills and ultimately the environment.
Typically, waste streams are composed of a variety of types of waste materials. One such waste stream is generated from the recovery and recycling of automobiles or other large machinery and appliances. For example, at the end of its useful life, an automobile will be shredded. This shredded material can be processed to recover ferrous metals. The remaining materials, referred to as automobile shredder residue (ASR) typically would be disposed in a landfill. Recently, efforts have been made to recover additional materials from ASR, such as plastics and non-ferrous metals. Similar efforts have been made to recover materials from whitegood shredder residue (WSR), which are the waste materials left over after recovering ferrous metals from shredded machinery or large appliances. Other waste streams may include electronic components, building components, retrieved landfill material, or other industrial waste streams. These materials generally are of value only when they have been separated into like-type materials. However, in many instances, cost-effective methods are not available to effectively sort waste streams that contain diverse materials. This deficiency has been particularly true for non-ferrous materials, and particularly for non-metallic materials, such as high density plastics, and non-ferrous metals, including copper wiring. For example, one approach to recycling plastics has been to station a number of laborers along a sorting line, each of whom manually sorts through shredded waste and manually selects the desired recyclables from the sorting line. This approach is not sustainable in most economies because the labor cost component is too high. Also, while ferrous recycling has been automated for some time, mainly through the use of magnets, this technique is ineffective for sorting non-ferrous materials. Again, labor-intensive manual processing has been employed to recover wiring and other non-ferrous metal materials. Because of the cost of labor, many of these manual processes are conducted in other countries and transporting the materials to and from these countries adds to the cost.
Copper wiring and other valuable non-ferrous metals can be recovered and recycled. However, waste materials, including ASR and WSR, must be separated from a concentrated mass of recoverable materials. Typically, the waste materials will include wood, rubber, plastics, glass, fabric, and copper wiring and other non-ferrous metals. The fabric includes carpet materials from the shredded automobiles. Often, the fabric includes embedded ferrous materials accumulated during the shredding process. Methods are known for separating the non-ferrous metals from these other materials. These methods may include a “pre-concentration” process that roughly separates the materials for further processing. However, these methods typically involve density separation processes. These processes typically involve expensive chemicals or other separation media and are almost always a “wet” process. These wet processes are inefficient for a number of reasons. After separation, often the separation medium must be collected to be reused. Also, these wet processes typically are batch processes, and they cannot process a continuous flow of material.
Another known system uses an air aspirator, or separator, to separate a light fraction of materials, which typically contains the waste materials that are not worth recovering (that is, the wood, rubber, and fabric), from a heavy fraction of materials, which typically includes the metals to be recovered. These types of separators are known in other industries as well, such as the agricultural industry, which uses air separators to separate materials of differing densities. However, these known systems usually employ open systems, where air is moved through the system and then released to the atmosphere. One problem with these systems is that they need air permits to operate, which adds cost to the system.
Conventional systems also force air directly up from a bottom of the plenum, and the material being separated falls on top of a screen at the bottom of the plenum. Accordingly, such systems cannot process heavy materials because the heavy materials will damage the screen when those materials fall on top of the screen.
Accordingly, a need exists in the art for a system and method that processes materials to be separated while recycling air in a closed system. Additionally, a need exists for a system and method that can separate heavier materials without damaging the system.